Multiple anthelmintic resistance decision support

More and more sheep farmers are testing for anthelmintic resistance, which is great news. But, if you are facing results that indicate there is resistance to two or more of the wormer groups on your farm, what should you do?

Don’t panic is the first piece of advice. The results can initially look daunting but in most cases the situation is not bleak, and there is certainly no need to assume you can no longer use Group 1, 2 or 3 wormer products. For most farms, a close look at the results, and testing at different times of year, will show the older three groups can still be used at certain times.

If testing shows the early stages of anthelmintic resistance (AR), there are a number of actions farmers can take to slow down its development. Examples include reducing the use of wormers by implementing options such as targeted treatments, grazing management and ensuring every dose is given accurately.

To help guide farmers through the key questions around multiple resistance SCOPS has put together a Decision Support Tree designed to provide you with options and actions to work through with your vet or animal health advisor.

Management options

• Develop a parasite control plan with your vet/animal health advisor
• Adopt stringent and effective quarantine for new and returning stock (Guidance effective-quarantine-and-treatments_1.pdf (scops.org.uk))
• Check anthelmintic efficacy every time they are used (provides the best option for optimising use, but any testing for efficacy of these drugs is better than none. It may be that drugs are still useful at different times of the year when different roundworms predominate on farm) Testing for Resistance | Worms | SCOPS
• Monitor performance and grazing history to develop a risk map of your farm which can help reduce treatment frequency

Reduce reliance on anthelmintics – reduce frequency of administration where possible

• Target treatment effectively (targeted treatments/targeted selective treatments) 2-2-preserve-susceptible-worms.pdf (scops.org.uk)
• Monitor flock regularly to determine treatment need and product efficacy
• Use forecasting tools (parasite and weather) to improve treatment timing
• Develop risk map (understand risk on paddocks on your farm) 2-4-2-pasture-based-risk-assessment.pdf (scops.org.uk)
• Grazing management
  • Integrate different host species
  • Use non-pregnant ewes to clean pasture
  • Use rotational grazing/cellular grazing
• Pasture management 2-4-4-graze-forages-with-anthelmintic.pdf (scops.org.uk)
  • Reseed (this may not fully resolve the issue but will help reduce contamination)
  • Use bioactive forages
• Breeding for worm resistance/resilience (EBVs but takes time to see results) 2-4-3-breeding-for-parasite-resistance.pdf (scops.org.uk)
• Maintain body condition scores for ewes within target range (AHDB link..)
• Monitor lamb performance against your own expectations and targets